Numerous types of production, packaging and printing machinery require accurate synchronization of rotating elements to insure optimum machine performance. Such timing relationships are often accomplished by start and stop, trial and error adjustments. However, this is time consuming and usually produces inexact results A preferred procedure is to make such timing adjustments while the machinery is running and there are various mechanisms available to provide mechanical, while-running rotary position control. Typically, such mechanisms constitute phase controlling transmissions or gear boxes which are capable of adjusting the phase angle relationship of rotatable elements such as input and output shafts. Generally, such transmissions have taken the form of a differential gear train employing a cage moveable about the input and output shafts and coupled to the latter by intervening bevel and pinion gears. Rotatable shifting of the cage serves to rotatably shift the gears to adjust the phase or angular relationship of input and output shafts coupled thereto. Typifying transmissions of this order is that disclosed in U.S. Pat. No. 3,563,104 issued Feb. 16, 1971, to Schuster.
Such prior known devices are characterized by a serious drawbacks. Inasmuch as the differential bevel and pinion gear train employed are in constant rotation in order to transmit power between input and output shafts, speed of adjustment and operation are seriously limited accompanied by excessive heat, wear, noise, power loss and limited life span. In addition, the phase controlling transmissions typified by the aforesaid U.S. Pat. No. 3,563,104, for example, are cumbersome structures embodying heavy gear trains.
A more recent development, as set forth in U.S. Pat. No. 4,832,658 issued May 23, 1981 to the assignee hereof, overcomes many of the difficulties of the previously known phase controlling transmissions or gear boxes by eliminating the heavy pinion and bevel gears through the use of unique helical spline connections between input and output shafts that provide a smooth, quiet, cool running, positive acting and long life mechanism in which either shaft may be used as the input shaft and in which the input and output shafts rotate in the same direction at a one to one ratio and are capable of phase adjustment while running or at rest.
Both of the above referred to developments of the prior art, while successful for their intents and purposes, are nevertheless characterized by certain inherent inaccuracies in adjustment due to the presence of back lash in the gear trains involved in their structure, although the helical spline gear train of the U.S. Pat. No. 4,832,658 is less susceptible to that criticism and defect. Nevertheless it has been a long felt desire of the makers and users of such phase adjusting devices to provide a mechanical, while-running or stationary rotary position control, capable of high torque transmission with essentially zero back lash.